Dynamic expression of lunatic fringe suggests a link between notch signaling and an autonomous cellular oscillator driving somite segmentation.

The metameric organization of the vertebrate trunk is a characteristic feature of all members of this phylum. The origin of this metamerism can be traced to the division of paraxial mesoderm into individual units, termed somites, during embryonic development. Despite the identification of somites as the first overt sign of segmentation in vertebrates well over 100 years ago, the mechanism(s) underlying somite formation remain poorly understood. Recently, however, several genes have been identified which play prominent roles in orchestrating segmentation, including the novel secreted factor lunatic fringe. To gain further insight into the mechanism by which lunatic fringe controls somite development, we have conducted a thorough analysis of lunatic fringe expression in the unsegmented paraxial mesoderm of chick embryos. Here we report that lunatic fringe is expressed predominantly in somite -II, where somite I corresponds to the most recently formed somite and somite -I corresponds to the group of cells which will form the next somite. In addition, we show that lunatic fringe is expressed in a highly dynamic manner in the chick segmental plate prior to somite formation and that lunatic fringe expression cycles autonomously with a periodicity of somite formation. Moreover, the murine ortholog of lunatic fringe undergoes a similar cycling expression pattern in the presomitic mesoderm of somite stage mouse embryos. The demonstration of a dynamic periodic expression pattern suggests that lunatic fringe may function to integrate notch signaling to a cellular oscillator controlling somite segmentation.

Aulehla A ，Johnson RL 《DEVELOPMENTAL BIOLOGY》

Periodic notch inhibition by lunatic fringe underlies the chick segmentation clock.

Dale JK ，Maroto M ，Dequeant ML ，Malapert P ，McGrew M ，Pourquie O ... -  《NATURE》

lunatic fringe is an essential mediator of somite segmentation and patterning.

Evrard YA ，Lun Y ，Aulehla A ，Gan L ，Johnson RL ... -  《NATURE》

Defects in somite formation in lunatic fringe-deficient mice.

Zhang N ，Gridley T 《NATURE》

Dynamic expression and essential functions of Hes7 in somite segmentation.

Bessho Y ，Sakata R ，Komatsu S ，Shiota K ，Yamada S ，Kageyama R ... -  《GENES & DEVELOPMENT》